Microinjection is a well-established cellular manipulation technique that enables introduction of exogenous materials into a cell through insertion of an extremely fine hollow needle. When working with non-adherent cells, conventional microinjection instrumentation typically requires an operator to locate the cell to be manipulated using an optical microscope and then capture it using aspiration (i.e. suction) from a blunt-tipped micropipette attached to a manually controlled micromanipulator. Using a separate manually-controlled micromanipulator, the operator then guides the needle towards the captured cell and inserts it for injection. Once completed, the operator retracts the needle and releases the cell by reversing the direction of aspiration flow. This procedure is then repeated in a serialized manner until sufficient numbers of cells have been manipulated for the intended application.
While microinjection is widely used in the engineering of cell lines, oocytes, and embryonic stem cells for transgenic animal generation and in vitro fertilization, its reliance upon skilled labor nonetheless limits its availability, since new operators require many months of training to develop proficiency. Moreover, the combination of manual operation and serialized injection methodology limits throughput (˜3 cells/min and 100-1,000 cells/day, depending on the cell type and operator skill), which constrains progress in many current applications, and precludes use in others where microinjection may otherwise hold great promise.